In next-generation vehicles, such as hybrid vehicles and electric vehicles, the heat generation density increases with the increase of the output of and decrease of the size of storage batteries and power devices. Thus, measures need to be taken against radiation of the generated heat. In addition to the next-generation vehicles, the same problem arises in transporters such as airplanes, LED luminaires, personal computers, household electric appliances, such as refrigerators, and any other devices that require electric power.
Due to such recent circumstances, it has become important to improve heat radiation performance of heat sinks and the like. In general, copper or aluminum is used as a metal heat radiation material for heat sinks. Extrusion or forging is employed as a production method. However, the improvement in performance by elaborate heat sink fin designs, that have been carried out so far, have substantially reached their limit from the viewpoint of, for example, workability and thermal resistance. Furthermore, extrusion and forging have a low degree of freedom in shape due to problems attributable to their production methods and also their required high cost. This makes it difficult to employ extrusion and forging methods.
Accordingly, various materials have been proposed that are used for heat sink fins. The materials have high thermal conductivity and thus produce an excellent heat-radiating effect. For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2006-63420, an aluminum alloy is proposed with high strength and high thermal conductivity. It is obtained by die casting a material containing silicon (Si), magnesium (Mg), iron (Fe), and boron (B) as additives, with the balance being aluminum (Al) and unavoidable impurities. Aging heat treatment is then performed.